From 7568b5719e357ebd97a685785237d5155b2c6504 Mon Sep 17 00:00:00 2001
From: "Alan T. DeKok" <aland@freeradius.org>
Date: Wed, 27 May 2020 09:57:08 -0400
Subject: [PATCH] add API to get ethernet address from interface

---
 src/lib/util/inet.c | 58 +++++++++++++++++++++++++++++++++++++++++++++
 src/lib/util/inet.h |  1 +
 2 files changed, 59 insertions(+)

diff --git a/src/lib/util/inet.c b/src/lib/util/inet.c
index 8b76ad0e2b..4152c4645b 100644
--- a/src/lib/util/inet.c
+++ b/src/lib/util/inet.c
@@ -34,6 +34,20 @@
 #include <sys/types.h>
 #include <ifaddrs.h>
 
+#ifdef HAVE_LINUX_IF_PACKET_H
+#  include <linux/if_packet.h>
+#  include <linux/if_ether.h>
+#endif
+
+#include <net/if_arp.h>
+
+/*
+ *	Apple, *BSD
+ */
+#ifndef __linux__
+#include <net/if_dl.h>
+#endif
+
 bool fr_reverse_lookups = false;		//!< IP -> hostname lookups?
 bool fr_hostname_lookups = true;		//!< hostname -> IP lookups?
 
@@ -1403,3 +1417,47 @@ int fr_interface_to_ipaddr(char const *interface, fr_ipaddr_t *ipaddr, int af, b
 	freeifaddrs(list);
 	return rcode;
 }
+
+/*
+ *	AF_PACKET on Linux
+ *	AF_LINK on BSD
+ */
+#ifndef AF_LINK
+#define AF_LINK AF_PACKET
+#endif
+
+int fr_interface_to_ethernet(char const *interface, uint8_t ethernet[static 6])
+{
+	struct ifaddrs *list = NULL;
+	struct ifaddrs *i;
+	int rcode = -1;
+
+	if (getifaddrs(&list) < 0) return -1;
+
+	for (i = list; i != NULL; i = i->ifa_next) {
+		if (!i->ifa_addr || !i->ifa_name || (i->ifa_addr->sa_family != AF_LINK)) continue;
+		if (strcmp(i->ifa_name, interface) != 0) continue;
+
+#ifdef __linux__
+		struct sockaddr_ll *ll;
+
+		ll = (struct sockaddr_ll *) i->ifa_addr;
+		if ((ll->sll_hatype != 1) || (ll->sll_halen != 6)) continue;
+
+		memcpy(ethernet, ll->sll_addr, 6);
+
+#else
+		struct sockaddr_dl *ll;
+
+		ll = (struct sockaddr_dl *) i->ifa_addr;
+		if (ll->sdl_alen != 6) continue;
+
+		memcpy(ethernet, LLADDR(ll), 6);
+#endif
+		rcode = 0;
+		break;
+	}
+
+	freeifaddrs(list);
+	return rcode;
+}
diff --git a/src/lib/util/inet.h b/src/lib/util/inet.h
index 638b033f08..e6db8c07e0 100644
--- a/src/lib/util/inet.h
+++ b/src/lib/util/inet.h
@@ -141,6 +141,7 @@ int	fr_ipaddr_from_ifindex(fr_ipaddr_t *out, int fd, int af, int if_index);
 char	*fr_ipaddr_to_interface(TALLOC_CTX *ctx, fr_ipaddr_t *ipaddr);
 int	fr_interface_to_ipaddr(char const *interface, fr_ipaddr_t *ipaddr, int af, bool link_local);
 
+int	fr_interface_to_ethernet(char const *interface, uint8_t ethernet[static 6]);
 /*
  *	Comparison
  */
-- 
2.47.3